A single-photon emission computed tomography (SPECT) agent 99mTc-HMDP and a positron emission tomography (PET) agent 18F—NaF are considered to be chemically absorbed mainly in hydroxyapatite crystals, which is the basic composition of bone minerals. Thus, a larger amount of such agents is absorbed in osteoblastic parts with increased bone turnover, allowing visualization of bone metastases of malignant tumors or inflammatory sites such as fractures, as areas of high accumulation of the agents.
The SPECT agent 99mTc-HMDP is promptly distributed to bone tissues in the whole body after it is administered intravenously, and yields high-quality bone scintigrams one to two hours after the administration.
The PET agent 18F—NaF has reportedly yielded stable bone scintigrams in 30 minutes after the administration. PET allows precise correction of an decrease or scatter of agents within the body, which enables provision of highly quantitative images.